This invention relates to a method and apparatus of deflection calibration or a charged particle beam exposure apparatus in which a charged particle beam such as an electron beam or an ion beam is directed at a high speed toward an object to expose the object to the beam for "writing" a desired pattern on the object with high precision.
A charged particle beam exposure apparatus as described above includes generally electromagnetic deflection means and electrostatic deflection means as means for deflecting the charged particle beam. Both of the electromagnetic deflection means and the electrostatic deflection means are jointly used in such an apparatus to obviate such defects that, when a field to be exposed to the beam which "writes" a desired pattern thereon is scanned with the electromagnetic deflection means alone, the beam deflection speed, hence, the writing speed is limited to a low value due to the hindrance such as an eddy current or a hysteresis phenomenon, while when such a field is scanned with the electrostatic deflection means alone, an excessive deflection astigmatism or the so-called sharpless beam concentration is inevitable. These problems are discussed in, for example, "The Electrochemical Society INC. Spring Meeting, St. Louis Mo.", May 11-16, 1980, extended Abstract p. 601 and "J. Vac. Sci. Technology," 16(6) November/December, 1979, p. 1686. Reference is to be made to these papers for details.
According to the prior art method relying on movement of a stage structure carrying an object to be subjected to charged particle beam exposure, for the purpose of deflection calibration for a charged particle beam exposure apparatus including deflection means as above described, the stage structure must be moved a multiplicity of times in required directions, as explained later with reference to the drawings, and, therefore, a long period of time is required for the above operation. Further, heat generated during the movement of the stage structure causes the distance between the fiducial mark and that portion of the stage structure which represents the portion of the stage structure to be measured by a laser interferometer to change and degrades the calibration precision, with a result that the lithography precision of the apparatus is greatly degraded.